A direct in vitro binding assay which is sensitive and quantitative for detection of specific antigens on the surface of cultured human urogenital tumor cells has been developed in our laboratory. The immunoglobulin (IgG) fractionated from rabbit antisera is radiolabeled with 125I to obtain sensitivity in measuring the antigens present on the test cells. Adsorption of IgG with normal non-urogenital tissue enables the detection of both organ specific antigens (OSA) and tumor associated antigens (TAA). Further adsorption with normal urogenital tissue allows the detection of TAA. This assay will be compared with two other sensitive and quantitative binding assays for detection of specific surface antigens. The most effective assay will be used to monitor the isolation of membrane associated OSA and TAA from human urogenital tumor tissues grown in athymic nude mice and from tissues obtained at surgery and autopsy. Purified antigens will be used for the preparation of specific antisera requiring minimal adsorption. The purified antigens will also be used to develop direct and blocking radioimmunoassays for detection of TAA and OSA in body fluids. Clinical testing will begin when quantitative adsorption experiments indicate that the adsorbed antibodies are specifically detecting OSA or TAA. Serum and urine from patients with different stages of urogenital malignant diseases will be tested for their ability to block the binding assay. The degree of blocking will indicate the amount of OSA and TAA in these body fluids. This information will be used to evaluate the binding assay as a method for early detection and monitoring of urogenital malignancies.